In the conventional variable speed drive in which a drive pulley and a driven pulley are each made up of a disc fixed against axial movement on a shaft and a disc which is movable axially with respect to the fixed disc, on the same shaft, the driven pulley movable disc is biased axially toward the fixed disc by a compression spring. The drive pulley movable disc is forced toward the fixed drive pulley disc mechanically. A V-belt running between the drive pulley and the driven pulley is forced radially outwardly from the center of the drive pulley when the movable disc of the drive pulley is forced toward the fixed disc of the drive pulley, which in turn, pulls the belt in a direction away from the driven pulley, forcing the movable disc of the driven pulley away from its associated fixed disc, against the bias of the spring.
It can be seen that under these circumstances, the faster the driven pulley rotates, i.e., the closer to the center of the pulley the belt moves, the greater the axial thrust of the movable disc will be, as the compression spring is compressed to a greater degree.
This produces excessive wear, and has no corresponding advantage, because the operation of the device does not require greater axial pressure on the belt at the higher speed.
One of the objects of the invention is to provide means and method for relieving a portion of the excess axial thrust of the compression spring as the speed of the driven pulley is increased.
Another object is to provide such means and method which are simple, dependable and effective.
Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawings.